In recent years, in the production of semiconductor devices or liquid-crystal-display elements, down-sizing has rapidly progressed as the lithographic technology advances. In general, as a method for down-sizing, wavelength of an exposure light source is shortened. Specifically, KrF excimer laser (248 nm) and ArF excimer laser (193 nm) are introduced now, although the ultraviolet rays represented by g line or i line were used conventionally.
As a resist for use in such an excimer laser, a chemically amplified resist composition which satisfies the conditions for high resolution which can reproduce a fine pattern is known, and the resist consists of a base resin having alkali solubility which changes by an action of acid, and an acid generator which generates an acid upon being exposed, as the basic components. The above chemically amplified resist composition involves both a negative type which contains an acid generator, a cross-linking agent, and an alkali-soluble resin as a base resin, and a positive type which contains an acid generator and a resin of which alkali solubility increases by the action of acid.
Hitherto, in the KrF excimer laser lithography, as a base resin of a chemically amplified resist, polyhydroxy styrene having a high transparency to a KrF excimer laser (248 nm) and a derivative therefrom obtained by protecting its hydroxyl group with an acid-dissociable, dissolution-inhibiting group (protecting group) has been generally used.
Furthermore, down-sizing of semiconductor devices has progressed increasingly, development of processes using an ArF excimer laser (193 nm) has been furthered energetically, and resists for use in ArF having various compositions have been proposed. Among them, an acrylic type resin with a high transparency at near 193 nm is known well as a base resin of the most general resist for use in ArF. As the above acrylic type resin, since it excels in dry etching resistance, the resin which has, as a main chain, the structural unit derived from (α-lower alkyl) acrylic ester [(α-lower alkyl) acrylate] which contains polycyclic and alicyclic saturated hydrocarbon groups such as an adamantane structure as an acid-dissociable, dissolution-inhibiting group at its ester part (side chain part) is generic (for example, see Patent document 1).
[Patent document 1] Japanese Unexamined Patent Application, First Publication No. H10-161313 official report
However, there is a problem in that the acrylic type resin containing an acid-dissociable, dissolution-inhibiting group which consists of a polycyclic and alicyclic saturated hydrocarbon group such as the above adamantane structure is expensive. Therefore, in the positive type resist composition using acrylic type resin, cost reduction and dry etching resistance are needed.
Moreover, in the ion implantation process, a positive type resist composition which can reduce cost and which excels in barrier properties of ions and destructive resistance of the resist pattern is needed.
The present invention is made in order to solve the above subjects, and it is an object of the present invention to realize cost reduction and dry etching resistance in the positive type resist composition using acrylic type resin. Moreover, it is another object of the present invention to improve the barrier properties of ions and the destructive resistance of a resist pattern in an ion implantation process, while maintaining low cost.